1. Field of the Invention
The present invention relates to a resin molding with an embedded coil for use in an electromagnetic valve designed for service in a hydraulic control circuit for a vehicular transmission and, more particularly, to protection of the leads of the coil device to be used in a linear solenoid.
2. Description of the Prior Art
A resin molding and coil device according to the prior art is shown in FIGS. 13 and 14. It is prepared by winding an electromagnetic coil 2 on a coil bobbin 1 and connecting a connector terminal 4 and an earth terminal 5 with the ends of the bobbin 1. Moreover, the connector terminal 4 and the earth terminal 5 have their individual fusing portions 6 connected to the leads 3 of the electromagnetic coil 2. The electromagnetic coil 2 thus wound is wrapped around its outermost circumference with an insulating tape (although not shown). The electromagnetic coil device thus assembled has its connector terminal 4 bent 90.degree. (as indicated by dotted lines in FIG. 13). Next, the device is covered over its entire surface, excepting portions of the connector terminal 4 and the earth terminal 5, with a molding resin 7 so that the resin molding with an embedded coil is produced.
In the prior art structure described above, however, the leads 3 of the electromagnetic coil 2 and the fusing portions 6 of the connector terminal 4 and the earth terminal 5 are in direct contact with the molding resin 7. Because the leads 3 and the molding resin 7 have different coefficients of thermal expansion the device is subject to thermal shock. As a result, excessive force is received by the connections between the leads 3 and the terminals 4, which connections have low tensile strength, thus risking breakage of the leads 3.
Especially in the case of a resin molding and coil device for use in an electromagnetic valve to be mounted in a vehicle for controlling a hydraulic circuit, the molding resin 7 is exposed to high temperature and a harsh atmosphere. Hence, a need exists in the art for improvement of the protection for the leads 3 of the electromagnetic coil 2.